Optogenetics has been widely used in the study of neural activity and behavior. By using genetic tools to target light-sensitive proteins to one or populations of neurons in specific region of brain, we can active those neurons by optical stimulation.
The foundation of neuron interaction bases on the ion transmission through the neuron membrane. The positively charged ions and negatively charged ions flow across the membrane via the transmission proteins and the balance of these ions in both inside and outside of the neurons contribute to the neurons trigger action potential. The action potentials, as known as spikes, are the key points in neural communication. Therefore, if we control the transmission proteins by genetic methods, then we can control the transmission of ions flow, which means that we can control the neurons communication.
Recently, the conventional way to achieve optogenetics is introducing light via optical fibers. However, light delivered by optical fibers is not at high spatial resolution in the brain because of light absorption and scattering. Therefore, Robert et al., show a novel optogenetic probe that achieves cell-type-specific perturbation precisely at high spatial resolution. The probe presented in the paper integrates micro-LEDs so that the light source is brought into the deep brain which allows high-spatial stimulation. Also the dimension of probe is small enough to minimize insertion damage. Unlike other similar approaches, the micro-LEDs are fabricated on silicon substrate, not on sapphire substrate. Sapphire-based LEDs cannot be thinned beyond 100 mm but silicon substrate can be thinned to a proper size that suitable for the probe. Therefore, the probe is able to reach the deep region of brain without unnecessary damage. I think this novel probe offers a good opportunity to study the neuron communication.